Passports are being required more and more as you travel. On the cruise ships you must show a picture ID every time you board the ship - either a passport or a driver's licence.
At the airports you are being asked for the same thing, so why not spend the money and get a passport - so easy to do. It will save you a lot of trouble, no matter where you travel.

I agree with Dizy. It's just a lot easier and a lot less hassle to have your passport. Tho' the initial cost may seem high, remember, it's good for 10 years, so it's really a bargain! And just think, once you have it, you're ready to go anywhere in the world!

You won't need a passport. Following are the ID requirements for U.S. citizens directly from HA's web site:

Identification Requirements

IMPORTANT: Guests arriving at embarkation without proper documentation may not join the voyage and will not be entitled to a refund.

The following documents are required for U.S. citizens:

Europe, Panama Canal/Coastal, Asia, South America or Prinsendam cruises:
A passport valid for the duration of the cruise and necessary visas; expired passports are not acceptable.

Alaska, Caribbean, Mexico, Hawaii, or New England:
Either:
1) A valid passport; ~or~
2) Picture identification issued by an official government agency AND an original or certified copy of birth certificate; ~or~
3) Picture identification issued by an official government agency AND a U.S. naturalization certificate.

Please note: Although passports are not required for some cruises, we highly recommend that you carry one while traveling.